1857 the Bonn Lecture
In 1857, while professor of anatomy and physiology in Bonn, Herman
Von Helmholtz delivered one of a series of popular lectures. The
title of this lecture was The Physiological causes of Harmony
in Music and it presented to the laymen a concise background of
the nature of a musical tone as well as a clear description of
how the mechanisms of the ear worked to analyze this sensation.
The text of this lecture can be found in the Selected writings
of Herman Von Helmholtz . Edited and with an introduction by RussellKahn
Much of this lecture would later be adapted to his book "On the
Sensation of Tone". published in 1863. There are two areas of
particular interest that Helmholtz discusses in this lecture.
The ear and the nature of timbre.
The background information on the formation and propagation of sound waves, the range of audible sounds, wave form, and sympathetic vibration, is presented as a reference for both the physiological and physical contributions that Helmholtz makes in this lecture. This information sets the stage for Helmholtz to consider the ear. Focusing on the cochlea, with its two membranes and division into three sections,Helmholtz uses the, then, recent discoveries of Marchese Corti to present a compeling argument for how the ear analyses sound. Corti discovered microscopically small plates arranged like piano keys. Helmholtz says,"They are connected at one end with the fibers of the auditory nerve and at the other with the stretched membrane."(p91). Helmholtz goes on to describe the arches of the cochlea as being " spun round with innumerable fibrils, among which some nerve fibers can be recognized." He uses one more bit of physiology before he makes his final point. He explains the vestibule where recently discovered "nerves expand upon little membranous bags". He describes them as "stiff hairs" and goes on to suggest that these appendages are set into sympathetic vibration by the waves of sound which are conducted through the ear."(p91 ) At this point in the lecture Helmholtz speculates. He says, "After very careful consideration, I am led to think it very probable that every such appendage is tuned to a certain tone like the strings of a piano", and that like a piano string, each hairlike apppendage will sympathetically vibrate when a corresponding tone is sounded. In addition, a corresponding nerve fiber experiences a sensation that is then brought to the attention of the intellect. As Helmholtz says,"It is not enough for the auditory nerve to have a sensation. The intellect must reflect upon it."(p99).
The single most important discovery to come out of this lecture relates to the element of timbre or tone quality. This is the quality of a tone that gives it its distictive feature. It is the quality that alows us to recognize a clarinet sound as being distinct from the sound of a violin. In this lecture Helmholtz manages to describe the relationship between timbre and the upper partials present in a fundamental tone. It is the theory of harmonic overtones that he sets down in this popular lecture. He investigates and demonstrates the presence of upper patials through a variety of experiments. These include experimentts with plucked strings, sympathetically vibrating piano strings, glass resonators, and vowel sounds produced by the human voice. Through these experiments Helmholtz leads us into previously uncharted territory in the field of acoustics. The conclusions drawn from this work had far reaching implications in the history of music. The most fundamental concluscion being,"We always hear the tone of a string accompanied by a certain combination of upper partial tones. A diferent combination of such tones belongs to the tone of a flute, or of a human voice, or a dogs howl."(p99). With regard to the ear, Helmholtz makes it clear that we are capable of hearing these upper partials. What is important to the human, however, is recognizing the difference between the howl of a dog and the cry of a baby or the sound of a violin. It is of little practical use for a human to realize the octave or the ninth above the fundamental tone.Given that this is the case, Helmholtz says,"The upper partials are consequently thrown into that unanalyzed mass of peculiarities of a tone which we call its quality."(p99).
At this time, in the world of Western music, harmony was expanding into new regions. The composers, Brahms, Listz , and in particular Wagner , were exploring chromatic harmony. Tonal centers were being stretched to the limit and the extension of chords was taking hold. Were they incorperating the theory that Helmholtz was scientificaly describing? We also know that Wagner was exploring new combinations of instruments in his work . This stands out as a direct example timbral effects. Was this an influence of Helmholtzs work on the musical life of the time? We also know that in the 1870s, Wagner built Bayreuth, to this day it is considered one of the most acoustically perfect theatres ever built. Once more, was this influenced by Helmholtzs work? The answers to these questions seem to be a matter of speculation. We do however find a direct influence of Helmholtzs work on the history of music, although this did not occurr unitl forty years after the work was completed.In 1906, Thaddeus Cahill was working on a new instrument. This instrument, named the" Telharmonium" ,used the theory of harmonic overtones and their relation to timbre to electronically reproduce the sounds of familair instruments. By way of extension, the Telharmonium was also capable of producing sounds hitherto unheard of by the human ear. This simply would not have been possible with out the earlier work of Helmholtz.